Leo Elwood Allen (October 5, 1898 – January 19, 1973) was an American politician from Illinois.

Born in Elizabeth, Illinois, Allen's maternal grandparents were German immigrants and his paternal grandfather was from England.

He taught school in Galena, Illinois in 1922 and 1923 and was clerk of the circuit court of Jo Daviess County from 1924 to 1932.

Allen was elected as a Republican to the United States House of Representatives in 1932 and would be re-elected thirteen additional times, serving from March 4, 1933, to January 3, 1961.

[3][4] Allen declined to seek a fifteenth term in 1960 and retired in Galena, where he died on January 19, 1973.